1. Field of the Invention
The present invention relates to a SAW (surface acoustic wave) filter encapsulated in a ceramic package, and a ceramic package therefor.
2. Description of the Background Art
It is a common practice with a ceramic package for encapsulating a SAW filter to form pads on one of its opposite major surfaces. A SAW filter chip or wafer chip is affixed to the package by adhesion or similar technology with its one major surface carrying a pattern of electrodes facing upward. The pattern of electrodes, i.e., electrode strips are connected to the pads of the package by bonding wires. A lid is mounted on the top of the package and sealed by solder. The electrodes are printed on a substrate of piezo-electric material, such as LiTaO.sub.3.
The above-mentioned conventional ceramic package has a problem in that the adjustment of impedance is very difficult partly because the surface of the filter chip carrying the electrode pattern and facing upward is hermetically sealed in the package and partly because the electrode pattern itself is printed on LiTaO.sub.3 or similar fragile material.